1. Field of the Invention
The present invention relates to a light-emitting module that uses a light-emitting diode chip, for example, as a light source, and more specifically to a structure for maintaining favorable luminous efficacy by suppressing increase in temperature of a light-emitting diode chip. The present invention further relates to an illumination apparatus on which the light-emitting module is mounted on the apparatus main body.
2. Description of the Related Art
For example, light-emitting diodes have higher efficiency and longer life spans than existing light sources such as fluorescent lamps and incandescent lamps. With improvement in luminous efficacy of light-emitting diodes, various kinds of illumination apparatus that use light-emitting diodes as light sources have recently been commercialized.
A light-emitting module employing a light-emitting diode as a light source comprises a light-emitting diode chip that emits blue light, and a transparent sealing member containing yellow phosphor particles. The sealing member encases the light-emitting diode chip. The blue light emitted by the light-emitting diode chip excites phosphor particles when passing through the sealing member. Thereby, the blue light is wavelength-converted by the phosphor particles, and white light is radiated outside the light-emitting module.
In the conventional light-emitting module, heat is generated by loss caused when blue light is wavelength-converted by phosphor particles. Thereby, the phosphor particles increase in temperature, and the light-emitting diode chip also increase in temperature. The increase in temperature of the light-emitting diode chip causes decrease in luminous efficacy of the light-emitting diode chip, and sufficient optical output is prevented from being achieved.
To address this problem, in the illumination apparatus disclosed in Japanese Patent KOKAI Publication No. 2008-218238, a translucent panel including a fluorescent film is provided away from a plurality of light-emitting diodes. The translucent panel is formed of glass superior in heat radiation properties to resin, and includes a storing concave portion on a plane facing the light-emitting diodes. The fluorescent film is formed by applying a fluorescent substance to the storing concave portion.
According to the above-described configuration, since the fluorescent film is separated from the light-emitting diodes, even if heat is generated when light from the light-emitting diodes is wavelength-converted, the heat is not easily transferred to the light-emitting diodes. Further, the heat generated during wavelength conversion can be emitted outside of the illumination apparatus from the translucent panel. Accordingly, decrease in luminous efficacy of the light-emitting diodes is suppressed, and optical output is improved.
According to the illumination apparatus disclosed in the above-described Japanese Patent KOKAI Publication, the translucent panel including the fluorescent film is supported by a frame of the illumination apparatus body at an outer peripheral portion of the translucent panel away from the fluorescent film. In the above-described configuration, much of the heat generated by the fluorescent film during wavelength conversion is emitted only from the surface of the translucent panel, and the heat is easily trapped in the storing concave portion of the translucent panel. Accordingly, the above-described configuration is susceptible to improvement regarding how to emit heat caused by wavelength conversion efficiently.
A luminescent apparatus disclosed in Japanese Patent KOKAI Publication No. 2008-147610, for example, comprises a substratum including a plurality of light-emitting elements mounted thereon, a translucent phosphor sheet containing a phosphor material, and a frame interposed between the substratum and the phosphor sheet. The frame surrounds the light-emitting elements individually.
This luminescent apparatus is capable of wavelength-converting light radiated from the light-emitting elements using the phosphor sheet, and emitting the wavelength-converted light from the surface of the phosphor sheet. This luminescent apparatus, however, merely disclose efficiently converting light from the light-emitting apparatus using the phosphor sheet and efficiently reflecting light traveling back toward the substratum from the phosphor sheet outside the luminescent apparatus. In other words, the above-described document does not mention a concrete structure for emitting heat generated when the phosphor sheet has generated heat due to loss caused by wavelength conversion.